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Vascular » Cerebrovascular
Carotid-cavernous fistula and carotid artery aneurysm
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Presentation A 60 year old woman presented for sudden visual loss in the right eye, exophthalmos, chemosis and proptosis. Functional ophthalmologic examination revealed immobility of the right eye, weak pupillary reaction to the light, right axial exophthalmos and right proptosis.
 
 
 
Caption: Gray-scale ultrasound of the right orbit
Description: Normal appearance of the right eye bulb is seen. A unilocular anechoic elongated mass is seen on the posterior aspect of the eye bulb, extending to the tip of the orbit and producing dislocation of the optic nerve.
 
 
 
Caption: Color Doppler of the right orbit
Description: High velocity bi-directional flow with marked turbulence is noted within the retroocular mass. On pulsed Doppler, arterial pulsatile flow was noted within the mass which exhibited low impedance, indicative of a large arterio-venous communication.
 
 
 
Caption: Color Doppler of the anterior pole of the orbit
Description: Abnormal dilated tortuous vessels with craniofugal flow were noted on the superior wall of the anterior pole of the orbit. Craniofugal flow with maximal velocity above 2m/sec was recorded at the orbit tip.
 
 
 
Caption: Axial T2 weighted MR image
Description: A mass at the level of the right carotid siphon in the parasellar region and located along the course of the carotid is seen indenting the sphenoid sinus and the sella. A retroocular mass continuous with vessels in the anterior pole of orbit is seen.
 
 
 
Caption: MRA 3D non-contrast TOF protocol for arteries
Description: The mass at the carotid siphon is well observed and it is seen to continue with the internal carotid artery. The vessels in the anterior pole of the orbit are not visualized.
 
 
 
Caption: MRA 3D non-contrast TOF examination for veins
Description: Both the dilated anterior orbital vessels and the mass of the right carotid siphon are depicted.
 
Differential Diagnosis Carotid-cavernous fistula - suggested by the presence of enlarged orbital vessels with low impedance flow
Hypervascular ocular tumor - arterial feeders and enlarged draining veins are usually absent
Arteriovenous malformation
Cavernous orbital angioma
 
Final Diagnosis MRI confirmed the final diagnosis to be a carotid-cavernous fistula and a right carotid artery aneurysm.
 
Discussion Carotid cavernous fistulae represent a direct communication between the arterial flow of the carotid siphon and the venous compartment of the cavernous sinus 1, 2, 3.

Carotid cavernous fistulae can be classified by:
1. Etiology: as traumatic or spontaneous. The traumatic fistulae occur more frequently, (75% of cases), appearing after car accidents or after endovascular therapy. Spontaneous fistulae usually result from a ruptured carotid aneurysm, in collagen vascular disease, atherosclerotic disease, hypertension, or at childbirth 3.

2. Flow: high or low flow

3. Anatomy: direct and indirect, according to the arterial branch involved (internal carotid artery [ICA], meningeal branches of the internal carotid artery or external carotid artery [ECA]).
Barrow’s classification 4 divides the carotid cavernous fistulae into four types:
• Type A: a fistula between the intracavernous segment of ICA and the cavernous sinus
• Type B: a shunt between the dural branch of the ICA and the cavernous sinus
• Type C: a shunt between the meningeal branch of the ECA and the cavernous sinus
• Type D: a shunt between branches of the ICA and the ECA and the cavernous sinus 1, 4.
According to this classification our case is included in type A.

Young men are more likely to develop traumatic fistulae than others, presumably due to the increased incidence of trauma in this patient group.  Postmenopausal women are prone to develop spontaneous dural carotid cavernous fistulae 4.
The association between a carotid cavernous fistula and an ICA aneurysm, secondary to a cranio-cerebral trauma or caused by a connective tissue defect, is a rare occurrence 1. Our patient did not have a history of cranio-cerebral trauma. For this reason, we assume that her condition was caused by a connective tissue defect. 

On Doppler ultrasound, the alteration of ICA hemodynamics (decreased resistence index and increased blood flow volume) is considered an indirect arterial sign of carotid cavernous fistula. Indirect venous signs are represented by enlargment of the superior ophthalmic vein, with reversed or bidirectional flow associated with a systolic component and reversed flow in the supraorbitar vein, with high flow velocity and low resistance. Thickening and dislocation of the optic nerve and sometimes, superior ophthalmic vein thrombosis may also be observed. Ultrasound may be useful in avoiding angiography, the latter being the golden standard. Ultrasonography can also be used in the follow-up of patients with slow venous flow or patients treated by embolization 1, 5, 6, 7, 8, 9. In our case, orbital ultrasound revealed the bidirectional, turbulent flow with systolic component in the right superior ophtalmic vein and optic nerve dislocation.

Yu-Wei Chen, et al. proposed the division of Barrow’s type A carotid cavernous fistulae in two categories, based on the ultrasonographic features: type I direct carotid cavernous fistula and type II carotid cavernous fistula with aneurysm. Based on this classification, our case belongs to type A II.

The natural evolution of carotid cavernous fistulae includes increasing proptosis, cranial nerve palsies, loss of vision (due to central retinal vein occlusion or glaucoma), epistaxis and intracranial or subarachnoid hemorrhage.

Carotid cavernous fistula can be effectively treated by occluding the fistula with transarterially deployable detachable balloons with preservation of the internal carotid artery. In the event that the balloon cannot be fed through the fistula via a transarterial approach, detachable platinum coils are often deployed electrolytically via a transarterial route 4, 10, 11, 12.
 
Case References 1. Zu-Wei Chen, et al. Carotid and Transcranial color-coded duplex sonography in the different types of Carotid-Cavernous Fistula. Stroke; 2000; 331:701-706.
2. Bahar Zanik, et al. JUM; 2003; 22: 1107-1110.
3. Koenigsberg, Robert A. CC Fistula, eMedicine World Medical Library, December 2002.
4. Barrow DL, et al. J Neurosurg 1985 Feb; 62(2): 248-56.
5. Kilic T, et al. Acta Neurochir (Wien). 2001 Dec; 143(12): 1257-64.
6. Dudea S.M, et al. Revista Romana de Ultrasonografie, vol. 4, Nr. 3-4, 2002.
7. Dudea S. M. Ultrasonografie vascularã. Bucureºti, Editura Medicalã 2004, 541-548.
8. Spector RH. Am J Ophthalmol 1991 Jan 15; 111(1): 77-83.
9. Chynpransky M, et al. Csek Slov Oftalmol. 1997; 53(2): 112-6.
10. Wetzel SG, et al. AJR 2000 May; 174(5): 1293-5.
11. Wadlington VR, Terry JB. Crit Care Clin 1999 Oct; 15(4): 831-54.
12. Onizuca M, et al. Neurol Med Chir. 2003; 43(10): 477-82.
 
Technical Details We used a Medison Kretz Sonoace 8800 ultrasound machine with a 7.5-10 MHz linear transducer and a 1 Tesla General Electric machine for the MRI.
 
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